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Biomedical subjects

V McDonald

Publications and source records attributed to V McDonald.

At least 19 recordsLinked to original sources
PubMed2006

A potential role for interleukin-18 in inhibition of the development of Cryptosporidium parvum.

Accumulating evidence suggests that intestinal epithelial cells (IECs) constitutively express the immunoregulatory cytokine interleukin (IL)-18. IECs also serve as the host cell for the intracellular parasitic protozoan Cryptosporidium parvum. In the present study, C. parvum infection of a human enterocyte cell-line HCT-8 resulted in increased expression of IL-18 mRNA as measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR). IL-18 protein was detected in control uninfected cells and following infection there was increased expression as measured by enzyme-linked immunosorbent assay (ELISA). Gene expression revealed the presence of the IL-18 receptor subunits not only in cell-lines but also in freshly isolated IECs, suggesting that IL-18-mediated signalling events may contribute to epithelial host defence during infection. Recombinant IL-18 inhibited intracellular development of the parasite in HCT-8 and HT-29 cells. Increased expression of bactericidal antibiotic peptides LL-37 and alpha-defensin 2 by IL-18 in HCT-8 and HT-29 cells may represent one mode of action by which this pluripotent cytokine aids in limiting the development of intracellular pathogens such as C. parvum in the gastrointestinal tract.

Animals↗
PubMed2005

Nebulised hypertonic saline for cystic fibrosis.

BACKGROUND: Lung disease in cystic fibrosis is characterised by impaired mucociliary clearance. Hypertonic saline has been shown to enhance mucociliary clearance in vitro and this may act to lessen the destructive inflammatory process in the airways. OBJECTIVES: To investigate the effects of treatment with nebulised hypertonic saline on people with cystic fibrosis compared to placebo and or other treatments that enhance mucociliary clearance. SEARCH STRATEGY: 'We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register, comprising references identified from comprehensive electronic database searches, handsearches of relevant journals and abstract books of conference proceedings. Most recent search of the Trials Register: September 2004. SELECTION CRITERIA: All controlled trials assessing the effect of hypertonic saline compared to placebo or other mucolytic therapy, for any duration or dose regimen in people with cystic fibrosis of any age or severity. DATA COLLECTION AND ANALYSIS: Two authors independently reviewed all identified trials and all data collected. Trial quality was assessed along with allocation concealment. MAIN RESULTS: Fourteen controlled trials were identified. Nine trials met the inclusion criteria involving 235 participants with an age range of 6 years to 46 years. Two short-term trials of immediate effect on mucociliary clearance demonstrated that hypertonic saline increased isotope clearance compared to control. Lung function, measured by improvement in forced expiratory volume at one second (FEV1 litre per minute), was observed in four trials. When 3% to 7% saline was used in a volume of 10 ml twice-a-day, in comparison to placebo, hypertonic saline led to a significant increase in FEV1, weighted mean difference 12.20 (95%CI 4.28 to 20.10). Two further trials compared a similar concentration and volume of hypertonic saline to recombinant deoxyribonuclease. Over a three-week period one trial showed a non-significant difference, mean difference 1.60 (95% CI -7.96 to 11.16). However, in a further trial, after 12 weeks treatment in participants with moderate to severe lung disease, recombinant deoxyribonuclease led to a greater increase in FEV1 than hypertonic saline (5 ml twice-daily), mean difference 8.00 (95%CI 2.00 to 14.00). No serious adverse events were noted. AUTHORS' CONCLUSIONS: Nebulised hypertonic saline improves mucociliary clearance in short-term clinical trials and appears to increase lung function compared to control. In comparison to recombinant deoxyribonuclease it may be less effective at improving lung function after three months. Currently there is insufficient evidence to support the use of hypertonic saline as routine treatment for people with cystic fibrosis.

Administration, Inhalation↗
PubMed2005

Nitazoxanide for persistent diarrhoea in Zambian acquired immune deficiency syndrome patients: a randomized-controlled trial.

BACKGROUND: Adults with acquired immune deficiency syndrome and persistent diarrhoea in Zambia have intestinal infection, predominantly protozoa. AIM: To search for treatment which can be offered with minimal investigation, we carried out a double-blind, randomized-controlled trial of nitazoxanide (a drug with a range of activity against parasites and bacteria). METHODS: Patients with diarrhoea of 1 month duration or longer were randomized to receive nitazoxanide (1000 mg twice daily) or placebo for 2 weeks. End-points were clinical response, parasitological clearance and mortality. RESULTS: Two hundred and seven adults were randomized; 42 died during the study. The primary assessment of efficacy was made after 17 days. Clinical response was observed in 56 (75%) of 75 patients receiving nitazoxanide and 45 (58%) of 77 patients receiving placebo (P = 0.03). The rate of improvement was markedly higher in patients with CD4 counts under 50 cells/microL receiving nitazoxanide (P = 0.007). The benefit was largely restricted to the period when the drug was being administered. No difference was seen in parasitological clearance between the two groups. Mortality was 19% by 4 weeks of follow-up and did not differ with treatment allocation. CONCLUSIONS: Nitazoxanide given orally for 14 days was associated with clinical improvement in Zambian acquired immune deficiency syndrome patients with diarrhoea, especially those with very low CD4 counts.

Acquired Immunodeficiency Syndrome↗
PubMed2003

The role of Cryptosporidium parvum-derived phospholipase in intestinal epithelial cell invasion.

In the Cryptosporidium parvum-infected intestinal epithelial cell, the parasite occupies an unusual extracytoplasmic location at the luminal surface, but how the invading zoites interact with the host cell to achieve this niche is poorly understood. This study examined the role of secretory phospholipase A(2) (sPLA(2)), a known virulence factor for several pathogenic microorganisms, in establishing C. parvum intracellularly. Initially, it was established that there was sPLA(2) activity in homogenates of C. parvum oocysts. C. parvum reproduction in two human enterocyte cell lines was significantly reduced by a specific PLA inhibitor, p-bromophenacylbromide, and by sheep anti-sPLA(2) antibodies developed against PLA(2) of bee ( Apis mellifera) venom. Treatment of either C. parvum sporozoites or enterocytes with sPLA(2) derived from cobra ( Naja naja) venom before initiation of infection increased the numbers of intracellular parasites. Thus, C. parvum PLA(2 )may play an important part in establishing the parasite within the enterocyte.

Acetophenones↗
PubMed2001

Interferon gamma induces enterocyte resistance against infection by the intracellular pathogen Cryptosporidium parvum.

BACKGROUND & AIMS: Interferon (IFN)-gamma plays an important role in the immunologic control of infection by the protozoan enteropathogen Cryptosporidium parvum. We tested the hypothesis that IFN-gamma may directly inhibit infection of enterocytes by this pathogen. METHODS: HT-29, Caco-2, and H4 human enterocyte cell lines were grown in monolayers and incubated with IFN-gamma before exposure with C. parvum. IFN-gamma receptor expression in the cell lines was determined by Western blot analysis. RESULTS: IFN-gamma inhibited C. parvum infection of both HT-29 and Caco-2 cells but not H4 cells. Response to IFN-gamma was related to the expression of the IFN-gamma receptor in the respective cell lines. The effect of IFN-gamma was partially reversed by inhibition of the JAK/STAT signaling pathway. IFN-gamma mediated its action by at least 2 mechanisms: (1) inhibition of parasite invasion and (2) by modification of intracellular Fe(2+) concentration. No role for tryptophan starvation or nitric oxide synthase activity was found. TNF-alpha and IL-1beta also had anti-C. parvum activity but had no synergistic effect with IFN-gamma. CONCLUSIONS: IFN-gamma directly induces enterocyte resistance against C. parvum infection; this observation may have important consequences for our understanding of the mucosal immune response to invasive pathogens.

Animals↗
PubMed2000

Nebulised hypertonic saline for cystic fibrosis.

BACKGROUND: The lung disease in cystic fibrosis is characterised by impaired mucociliary clearance, recurrent bronchial infection and airway inflammation. Hypertonic saline has been shown to enhance mucociliary clearance in-vitro and this may act to lessen the destructive inflammatory process in the airways. OBJECTIVES: To determine if nebulised hypertonic saline treatment improved lung function, exercise tolerance, quality of life and decreased the incidence of exacerbations of respiratory infections in patients with cystic fibrosis. SEARCH STRATEGY: Studies were identified from the Cochrane Cystic Fibrosis and Genetic Disorders Group trials register. Titles and abstracts were reviewed to identify all controlled trials. Review articles and bibliographies identified from this process were surveyed for additional citations & RCTs. Identification of unpublished work was obtained from abstract books from the three major Cystic Fibrosis conferences (International Cystic Fibrosis Conference, The European Cystic Fibrosis Conference and the North American Cystic Fibrosis Conference). Trial authors were contacted for additional information when only abstracts were available to review. Date of the most recent search of the Group's specialised register: November 1999. SELECTION CRITERIA: All controlled trials that assessed the effect of hypertonic saline compared to placebo or other mucolytic therapy, for any duration or dose regimen in subjects with cystic fibrosis of any age or severity were reviewed. Studies in languages other than English were included. DATA COLLECTION AND ANALYSIS: All identified trials were independently reviewed by both reviewers & all data collected. Trial quality was scored by the Cochrane assessment of allocation concealment & the Jadad scale of methodological quality. MAIN RESULTS: Twelve controlled trials of hypertonic saline were identified. Seven trials met the inclusion criteria; these involved 143 subjects with an age range of 6 to 46 years. Of these, six were published studies and one in abstract form. The durations of the trials were limited to immediate effects on mucociliary clearance to a maximum of three weeks. In two studies, involving thirty five subjects, a score for the feeling of cleared chest was made using visual analogue scales. This analysis showed a weighted mean difference of -0.98 (95% confidence Interval -1.6, -0.34), favouring hypertonic saline over isotonic saline. In two trials with 22 subjects hypertonic saline improved mucociliary clearance as measured by isotope clearance from the lungs in 90 minutes demonstrating a weighted mean difference of -11.3 (95% confidence Interval -18.6, -4.0), and as area under the clearance time curve; weighted mean difference of -212 (95%CI -272, -152), also favouring hypertonic saline over isotonic saline. Lung function as measured by improvement in FEV1 was observed in one study of 27 subjects. The percentage increase in FEV1 at two weeks increased by a mean 15.0% with hypertonic saline and 2.8% with isotonic saline (p=0.004). Adverse events were adequately described in only one trial and none were serious. REVIEWER'S CONCLUSIONS: Nebulised hypertonic saline improves mucociliary clearance immediately after administration which may have a longer term beneficial effect in cystic fibrosis. The maximum time data were recorded for was only three weeks. Most of the patients had mild to moderate lung disease and the effect on severe lung disease remains unclear. Further studies of hypertonic saline should be carried out to determine the effect on pulmonary function tests, quality of life, frequency of exacerbations of respiratory disease and efficacy comparisons with nebulised deoxyribonuclease, with larger numbers and for longer duration. At this stage there is insufficient evidence to support the use of hypertonic saline in routine treatment for patients with cystic fibrosis.

Administration, Inhalation↗
PubMed2000

Host cell-mediated responses to infection with Cryptosporidium.

The coccidian Cryptosporidium infects epithelial cells of a variety of vertebrate hosts and is the causative agent of cryptosporidiosis. In mammals, including humans and domestic animals, C. parvum infects the gastrointestinal tract producing an acute watery diarrhoea and weight loss. CD4+ T-cell-deficient hosts have increased susceptibility to infection with the parasite and may develop severe life-threatening complications. The host responses which induce protective immunity and contribute to pathogenesis are poorly understood. In the immunological control of infection, recent studies with murine infection models suggest that IFN-gamma plays a key role in a partially protective innate immunity against infection identified in immunocompromised mice and also in the elimination of infection mediated by CD4+ T-cells. At the mucosal level, CD4+ intraepithelial lymphocytes are involved in the control of cryptosporidial infection, acting at least in part through production of IFN-gamma which has a direct inhibitory effect on parasite development in enterocytes. Primary infection of ruminants induces an intestinal inflammatory response in which increased numbers of various T-cell subpopulations appear in the villi. In addition, infection results in increased intestinal expression of pro-inflammatory cytokines such as IL-12, IFN-gamma and TNF-alpha. Because these cytokines appear to be important in the aetiology of inflammatory bowel disease, it is possible that they are involved in the mucosal pathogenesis of cryptosporidiosis.

Animals↗
PubMed1999

Gut intraepithelial lymphocytes and immunity to Coccidia.

Little is known about the physiological functions of the intra-epithelial lymphocytes (IELs) of mucosal tissues, including their role in immunity to infection. Most IELs are T cells, but their surface phenotype and activation characteristics are different from those of peripheral T cells. Here, Vincent McDonald outlines the distinctive features of IELs and presents evidence, particularly from studies of Coccidia, that these cells have an important role in the control of intracellular infection at the mucosal surface.

Animals↗
PubMed1999

The characteristics of asthma education programs within New South Wales.

The aim of the study was to examine the characteristics of asthma education programs within NSW. A cross-sectional questionnaire survey concerning the aims and characteristics of 42 asthma education programs was administered to members of the Asthma Educators Association (AEA) of NSW. While most programs sought to improve asthma knowledge (78%), only a small number sought to improve asthma management skills (38%), asthma control (33%) and attitudes (10%). Most programs performed one-to-one (69%) education. Medical intervention was under-utilized by most programs and only 4% gave feedback to the referring doctor. Program evaluation was incompletely linked to program aims. There was incomplete evaluation of knowledge gain as an outcome. The study reviewed the characteristics of education programs within NSW Existing programs appropriately employ a variety of educational methods and target a broad range of people with asthma. There remains a need to use a combined approach utilizing education and medical management, and to employ methods to evaluate programs.

Adolescent↗
PubMed1999

Transjugular intrahepatic portosystemic shunt (TIPS) for Budd-Chiari syndrome or portal vein thrombosis: review of indications and problems.

OBJECTIVE: The aim of this study was to evaluate the role of transjugular intrahepatic portosystemic shunt (TIPS) in patients who present with portal vein thrombosis (PVT) or Budd-Chiari Syndrome (BCS). METHODS: Nine patients with recent PVT and four patients with BCS underwent TIPS. The diagnosis was confirmed by color Doppler ultrasound and by angiogram in most patients. Patients were followed clinically and had TIPS checked periodically for patency. The end point was mortality, subsequent surgical shunting or orthotopic liver transplantation (OLT). RESULTS: TIPS was placed in 13 of 15 (87%) patients with BCS or PVT. The mean decrease in pressure gradient was 56%. Median and mean follow-up were 14 months and 16.9 months. Procedure related complications occurred in two of 13 (15%), both in the PVT group. Direct procedural mortality was one of 13 (8%). The majority of patients with PVT (five of eight) underwent OLT. Of the remaining three, one patient subsequently developed a cavernous transformation of portal vein but is stable, one patient is stable, without further variceal bleeding, and one patient died because of multiple organ failure. In patients with BCS, three of four (75%) did well with TIPS, but one patient required immediate surgical shunting after occlusion of the TIPS. Two patients underwent OLT and the fourth patient is stable 2 yr later but has cirrhosis on biopsy. CONCLUSIONS: In patients with BCS, TIPS placement is effective and can be used as a bridge to liver transplantation. TIPS in the noncavernous PVT group should only be recommended when cirrhosis and uncontrollable variceal bleeding are present.

Adult↗
PubMed1998

Characterisation of a Cryptosporidium parvum-specific cDNA clone and detection of parasite DNA in mucosal scrapings of infected mice.

A cDNA library was constructed using total RNA extracted from oocysts and sporozoites of the protozoan parasite Cryptosporidium parvum. The expression library was screened with an anti-C. parvum antiserum and a clone, Cp3.4, with a 2043 bp insert, was extracted. Southern blot analysis demonstrated a single copy gene that was located on a 1.6 Mb chromosome. The gene was found to be C. parvum specific as Cp3.4 did not cross-hybridise with chromosomal DNA from three other apicomplexan parasites. The cDNA encodes a polypeptide with a predicted membrane helix at its C-terminal end which is flanked by stretches of acidic amino acids. Overall, the polypeptide has a low isoelectric point (pI) of 3.94. A total of 21 glycine/proline-rich octapeptides were identified which represented variations of a consensus sequence. The function of this protein is yet unknown. Using Cp3.4-specific PCR primers, this C. parvum gene could be amplified from as little as 0.8 pg of purified parasite DNA in a single polymerase chain reaction. Less than 0.1 ng of DNA from the ileum mucosa of immunosuppressed adult mice that had been infected with C. parvum oocysts was required to detect the parasites. In non-immunosuppressed mice that were infected and which did not shed oocysts in numbers detectable by acid-fast staining, parasite development could be detected in 25 ng of total mucosa DNA. This PCR approach may be a valuable technique for the detection of parasite infections in situations where conventional staining methods fail, such as chronic, low-grade infections or the detection of parasites in potential reservoir hosts.

Amino Acid Sequence↗
PubMed1998

Androgen-behavior correlations in hypogonadal men and eugonadal men. II. Cognitive abilities.

Sex-typed cognitive abilities were assessed in 33 hypogonadal men receiving testosterone replacement therapy, 10 eugonadal men receiving testosterone in a male contraceptive clinical trial, and 19 eugonadal men not administered testosterone. Prior to and following hormone administration, men completed four tests measuring visuospatial ability, three tests measuring verbal fluency, two tests measuring perceptual speed, and a measure of verbal memory. Group differences in testosterone levels were unrelated to performance on most cognitive measures, including visuospatial ability. Relative to other men, hypogonadal men were impaired in their verbal fluency and showed improved verbal fluency following treatment with testosterone. These data suggest that testosterone may enhance verbal fluency in hypogonadal men and support the general hypothesis that current levels of testosterone may influence some aspects of cognitive function.

Adult↗
PubMed1998

Differentiation between human and animal isolates of Cryptosporidium parvum using molecular and biological markers.

Isolates of Cryptosporidium parvum obtained from infected humans, calves and lambs were typed using arbitrary primed polymerase chain reaction (AP-PCR) and isoenzyme electrophoresis. All animal isolates tested (n = 17) showed similar profiles in AP-PCR and isoenzyme typing. In AP-PCR assays, 9 out of 15 human isolates showed a distinct "human" profile while the remaining 6 isolates showed the "animal" profile. In isoenzyme typing, 5 human isolates which had shown "human" profiles in AP-PCR demonstrated a unique isoenzyme banding pattern, while 2 isolates which had shown "animal" profiles in AP-PCR gave the "animal" banding pattern. In a murine model of infection, all four animal isolates tested were highly infective but only one of four human isolates identified as "human" type in the AP-PCR and isoenzyme typing systems was infective. The good correlation between the data from the different typing systems supports the hypothesis that there are genetically distinct human and animal populations of C. parvum.

Animals↗
PubMed1998

Posture, locomotion, spatial orientation, and motion sickness as a function of space flight.

This article summarizes a variety of newly published findings obtained by the Neuroscience Laboratory, Johnson Space Center, and attempts to place this work within a historical framework of previous results on posture, locomotion, motion sickness, and perceptual responses that have been observed in conjunction with space flight. In this context, we have taken the view that correct transduction and integration of signals from all sensory systems is essential to maintaining stable vision, postural and locomotor control, and eye-hand coordination as components of spatial orientation. The plasticity of the human central nervous system allows individuals to adapt to altered stimulus conditions encountered in a microgravity environment. However, until some level of adaptation is achieved, astronauts and cosmonauts often experience space motion sickness, disturbances in motion control and eye-hand coordination, unstable vision, and illusory motion of the self, the visual scene, or both. Many of the same types of disturbances encountered in space flight reappear immediately after crew members return to earth. The magnitude of these neurosensory, sensory-motor and perceptual disturbances, and the time needed to recover from them, tend to vary as a function of mission duration and the space travelers prior experience with the stimulus rearrangement of space flight. To adequately chart the development of neurosensory changes associated with space flight, we recommend development of enhanced eye movement systems and body position measurement. We also advocate the use of a human small radius centrifuge as both a research tool and as a means of providing on-orbit countermeasures that will lessen the impact of living for long periods of time with out exposure to altering gravito-inertial forces.

Humans↗
PubMed1998

Graded testosterone infusions distinguish gonadotropin negative-feedback responsiveness in Asian and white men--a Clinical Research Center study.

Recently, multicenter clinical trials to determine male contraceptive efficacy disclosed that testosterone-induced suppression of spermatogenesis to azoospermia occurred in about 90% of Asian but only 60-70% of white men. To test whether there are ethnic differences in the sensitivity of gonadotropin secretion to suppression by testosterone, we administered constant infusions of testosterone at 0, 7, 14, and 28 mg/1.7 m2 x 24 h i.v. for 48 h to 9 Asian and 8 white normal male volunteers (22-42 yr old). During the last 8 h of each infusion dose, 10-min frequent blood sampling was carried out for later LH and FSH measurements by sensitive fluoroimmunoassays. Analyses of LH secretory pulses showed that LH pulse width, height, area, and total area under the curve (LH concentration vs. time) were significantly more suppressed in Asians than in whites during the lowest infusion dose of testosterone. With increasing testosterone dose, the suppression of pulsatile LH secretion was not different in the two ethnic groups. In contrast to pulsatile LH secretion, the responsiveness of pulsatile FSH secretion to exogenous testosterone infusion was not different between the two ethnic groups. At baseline, Asian men had a significantly higher mean number of FSH pulses and mean incremental pulse heights than did white men. Serum inhibin B levels were not distinguishable in the two ethnic groups, but the FSH profiles were quantifiably more irregular (higher approximate entropy) in the Asian volunteers. Our data suggest that, compared with white men, Asian men respond earlier and with more marked suppression of pulsatile LH secretion to ramped testosterone infusions. The elevated basal serum FSH concentrations (and more irregular FSH release pattern) observed in Asian men may suggest a small relative decrease in spermatogenic reserve and/or gonadal negative feedback. Whether these differences contribute to the observed differences in suppression of spermatogenesis in Asians vs. non-Asians in male contraceptive studies is not yet known.

Adult↗